Insulated heat dissipation substrate

1. An insulated heat dissipation substrate comprising: a ceramic substrate; and a conductor layer bonded onto at least one of main surfaces of the ceramic substrate, wherein the conductor layer comprises: an upper surface; a lower surface; and a side surface 1 connecting the upper surface with the lower surface; wherein the ceramic substrate comprises: a lowest portion; a side surface 2 connecting the lowest portion with the side surface 1 of the conductor layer; and a bonding surface at a position higher than the lowest portion, the bonding surface being bonded to the lower surface of the conductor layer; wherein, when the conductor layer and the ceramic substrate are observed in a cross section parallel to both of a normal direction relative to a tangential line of a contour of the conductor layer as viewed in plane and a thickness direction, an absolute value of a difference between an elevation angle α of the side surface 1 at the height of the lower surface relative to the lower surface and an elevation angle β of the side surface 2 at the height of the bonding surface relative to the bonding surface is 20° or less on average; and wherein, when the conductor layer and the ceramic substrate are observed in the cross section parallel to both of the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane and the thickness direction, the side surface 1 has a receding portion from an end of the upper surface in the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane.

2. The insulated heat dissipation substrate according to claim 1 , wherein, when the conductor layer and the ceramic substrate are observed in the cross section parallel to both of the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane and the thickness direction, the elevation angle α of the side surface 1 is from 20° to 60° on average.

3. The insulated heat dissipation substrate according to claim 1 , wherein a distance H between the lowest portion of the ceramic substrate and the end portion of the bonding surface in the thickness direction is from 0 μm to 30 μm on average.

4. The insulated heat dissipation substrate according to claim 1 , wherein, when the conductor layer and the ceramic substrate are observed in the cross section parallel to both of the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane and the thickness direction, each of contours of the side surface 1 and the side surface 2 has an inwardly recessed curve line.

5. The insulated heat dissipation substrate according to claim 1 , wherein, when the conductor layer and the ceramic substrate are observed in the cross section parallel to both of the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane and the thickness direction, a distance L from the lowest portion to the bonding end of the bonding surface in the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane is from 5 μm to 30 μm on average.

6. The insulated heat dissipation substrate according to claim 1 , wherein the most receding portion of the receding portion of the side surface 1 recedes 200 μm or less on average from the end portion of the upper surface in the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane.

7. The insulated heat dissipation substrate according to claim 6 , wherein the most receding portion of the receding portion of the side surface 1 recedes 20 μm or more and 100 μm or less on average from the end portion of the upper surface in the normal direction relative to the tangential line of the contour of the conductor layer as viewed in plane.